This invention relates to semiconductor electronic apparatus and more particularly to devices which employ tunneling of charges between coupled quantum wells.
The concept of tunneling in electronic devices has been around for many years. Tunnel diodes were discovered by Esaki in 1958 (L. Esaki, Phys. Rev., 109, 603 (1958)) and since then several three terminal electronic devices have been proposed and built. The known three-terminal tunneling devices, however, all involved tunneling through only one well rather than coupled wells as disclosed herein. The transmission of carriers perpendicular to potential wells has been considered in the literature, but these devices did not employ tunneling.
One known three terminal device is described in "A Field Effect Transitor With A Negative Differential Resistance" by Kastalsky et al. in IEEE Election Devices Letters, EDL-5, 57-60 (1984). The NERFET disclosed therein is a three-terminal device in which charge is transferred out of the source-drain channel by thermionic emission rather than through the tunneling process. Although the channel of the NERFET constitutes a quantum well, the charge transfer is likely to be much slower than with tunneling.
Another three-terminal device is described in "Velocity Modulation Transistor (VMT)--A New Field Effect Transistor Concept" by Sakaki in Japanese Journal of Applied Physics, Vol. 21, No. 6, pp. L381-L383, (June 1982). This article discloses a device with two channels having different mobilities. However, the transport taught by Sakaki is not tunneling but rather deformation of the barrier with charge transport over the barrier. Tunneling disclosed herein offers both higher transconductance and a higher cut-off frequency of operation.
It is, therefore, an object of the present invention to provide coupled quantum wells utilizing the tunneling process for extremely high speed electronics applications.
It is a further object of the invention to provide a three-terminal device capable of operating at terahertz frequencies.
Yet another object of the invention is a detector of radiation having millimeter and submillimeter wavelengths.
A still further object of the invention is structure utilizing the tunneling process for emitting photons of electromagnetic radiation.